Cache URLs for performance improvement.

Reviewed by me.

Objective-J/Executable.js

@@ -20,12 +20,12 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+
 var ExecutableUnloadedFileDependencies  = 0,
     ExecutableLoadingFileDependencies   = 1,
     ExecutableLoadedFileDependencies    = 2,
     AnonymousExecutableCount            = 0;
 
-
 function Executable(/*String*/ aCode, /*Array*/ fileDependencies, /*CFURL*/ aURL, /*Function*/ aFunction)
 {
     if (arguments.length === 0)
@@ -366,6 +366,9 @@ Executable.fileImporterForURL = function(/*CFURL*/ aURL)
     {
         cachedImporter = function(/*CFURL*/ aURL, /*BOOL*/ isQuoted, /*Function*/ aCallback)
         {
+            // We make heavy use of URLs throughout this process, so cache them!
+            enableCFURLCaching();
+
             aURL = new CFURL(aURL, isQuoted ? referenceURL : NULL);
 
             var fileExecutableSearch = new FileExecutableSearch(aURL, isQuoted);
@@ -377,6 +380,9 @@ Executable.fileImporterForURL = function(/*CFURL*/ aURL)
                     {
                         fileExecutable.execute();
 
+                        // No more need to cache these.
+                        disableCFURLCaching();
+
                         if (aCallback)
                             aCallback();
                     }